1. Field of the Invention
The present invention relates to a method of depositing a film.
2. Description of the Related Art
A manufacturing process of a semiconductor integrated circuit (IC) includes a process of forming a thin film on a semiconductor wafer. In this process, improvement in evenness of a surface of a wafer is required in view of further microminiaturization of an IC. As a method of depositing a film to satisfy this requirement, a method of depositing the film called an atomic layer deposition (ALD) method or a molecular layer deposition (MLD) method is considered. According to the ALD method, a cycle in which one (a reaction gas A) of two types of reaction gases, which mutually react, is caused to adsorb on the surface of the wafer, and the adsorbing reaction gas A is reacted with the other one (a reaction gas B) of the two types of reaction gases is repeated thereby depositing a thin film made of a reaction product onto the surface of the wafer. Because the ALD method uses the adsorption of the reaction gas onto the surface of the wafer, the ALD method has an advantage that film thickness evenness and film thickness controllability are excellent.
A turntable-type film deposition apparatus is disclosed in Japanese Patent No. 4661990 as a film deposition apparatus performing the ALD method. This film deposition apparatus includes a turntable, which is rotatable and is positioned in a vacuum chamber, and on which a plurality of wafers are placed, a separation area that is laid out above the turntable and separates a gas supply area for the reaction gas A from a gas supply area for the reaction gas B, evacuation ports corresponding to the gas supply areas where the reaction gas A and the reaction gas B are supplied, and an evacuation device connected to these evacuation ports. In this film deposition apparatus, the wafers pass through the gas supply area for the reaction gas A, the separation area, the gas supply area for the reaction gas B, and the separation area along rotation of the turntable. This causes the reaction gas A to adsorb on the surface of the wafer in the gas supply area for the reaction gas A and the reaction gas A to react with the reaction gas B in the gas supply area for the reaction gas B. Accordingly, it is not necessary to change the reaction gas A to the reaction gas B during the film deposition, and the reaction gases A and B can be continuously supplied. Therefore, there is an advantage that an evacuation/purge process is unnecessary thereby shorting a time period for depositing the film.
Meanwhile, along with higher integration of the semiconductor memory, a capacitor using a high-dielectric material such as a metal oxide as a dielectric layer is more frequently used. The electrodes of this capacitor are made of titanium nitride (TiN) having a relatively great work function. Thus, because titanium nitride is used as the electrodes, the titanium nitride is required to have a low-value resistance, and depositing a low-resistance thin film is required when depositing a thin film of titanium nitride.
The TiN electrodes are produced by depositing a TiN film on a high dielectric layer by a chemical vapor deposition (CVD) method using titanium chloride (TiCl4) and ammonia (NH3) as source gases and patterning the deposited TiN film as disclosed, for example, in Japanese Patent No. 4583764 and Japanese Patent No. 4811870.
Moreover, for example, depositing a film of titanium nitride by the ALD method is thought to be possible by using the above-mentioned turntable type film deposition apparatus, using titanium chloride and ammonia as the source gases, similarly to the CVD method.
However, the above-mentioned film deposition using the CVD method has difficulty depositing a dense film and a TiN film having a sufficiently low-value resistance.
On the other hand, in the above-mentioned ALD method, depositing a dense and low-resistance TiN film is possible because the film deposition of atomic layers or molecular layers in a layer-by-layer manner is possible. Furthermore, in the ALD method, a low-resistance film of another metal nitride is likely to be deposited.
However, in the film deposition of the TiN film, a different process is required from the film deposition of an insulating metal oxide film such as SiO2 that has been performed by using the ALD method. For example, in a film deposition process of TiN, a film deposition temperature and a cycle time for depositing one atomic layer or one molecular layer different from the film deposition of the metal oxide film are required instead of merely supplying different gases.